STEEL-SLAG AS SUBSTITUTE TO NATURAL AGGREGATES, PROPERTIES AND THE INTERFACIAL TRANSITION ZONE - Diponegoro University | Institutional Repository (UNDIP-IR) HAN AY LIE
STEEL-SLAG AS SUBSTITUTE TO NATURAL
AGGREGATES, PROPERTIES AND THE INTERFACIAL TRANSITION ZONE
Han Ay Lie *)
Abstract
Steel-slag is a residual product of the steel industry that has potential ability to pollute the ground water
and soil containing heavy metals. To overcome this problem, attempts have been made for using the slag as
substitute for both coarse and fine aggregates in concrete. The solidification process will prevent the metal
components from polluting the water and soil.
Test results on the mechanical properties of slag-concrete showed that while the compression strength of
slag-concrete increased significantly as a function of slag-to-natural aggregate’s use, the tensile strength
dropped accordingly.
The substitution of fine-slag to Muntilan sand was even more negative, the compression strength decreased
as a function of slag use. Research into the influences of the Interfacial Transition Zone was conducted,
since the ITZ itself forms a weak link within the concrete matrix.
The SEM tests were performed at the Quarter Laboratory, Department of Geology in Bandung using a
Scanning Electron Microscope type JEOL.
Keywords: slag, fine and coarse aggregates, compression and tensile strength.
Introduction
Research conducted at the Construction and
Material Laboratory, Civil Engineering Department, Diponegoro University (Han and Tudjono,
2008, 2007) concluded the following:
1. Workability of fresh concrete mixes increase
as a function of slag usage resulting in a more
compact concrete with a higher mass density.
2. 28 days compression strength increases as a
function of slag - to-conventiona l -aggregate
percentage (figure 1).
3. The ratio of tensile - to-norma l -concrete
strength decreases as a function of increase in
coarse slag usage (figure 2).
4. Fine slag influences both workability and
compression strength negatively.
Figure 2. Tensile Strength of Slag Concrete (Han,
Tudjono, 2008, 2007)
This research work was accomplished by substituting the Pudak Payung aggregates gradually
by the steel-slag, and by replacing the Muntilan
sand by fine slag. All specimens were tested at
age 28 days.
The deviation of compression-to-tensile-strengthrelation arouses the question as whether the cause
is originated from the nature of aggregates itself
and its Interfacial Transition Zone in concrete.
Figure 1. Compression Strength of Slag Concrete
(Han, Tudjono 2008, 2007)
Cement Hydration and the Interfacial Transition Zone
Concrete is a heterogenic material consisting of
aggregates embedded in a cement matrix. The
me-chanical properties of this material are
influenced by their interaction. Figure 3 shows
the physical appearance and the stress-strain
relationship of concrete making components.
*) Staf Pengajar Jurusan Teknik Sipil Fakultas
Teknik Undip
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
1
Figure 3a. Concrete Cross Sectio
Figure 3b. Stress-Strain relationship
of concrete components
The formation of concrete is a product of cement
hydration. Cement is a chemical component consisting of (CaO)3(SiO2) commonly noted as C3S,
(CaO)2(SiO2) noted as C2S and (CaO)3(Al2O3)
noted C3A (fig. 4).
The hydration process results in C-S-H, CH and
ettringite crystals are as following:
• 2C3S+11H?3CH+C3S2H8
• 2C2S+9H?CH + C3S2H8 or (C-S-H)
Calcium Silicate Hydrate
• C3A+3CSH2+26H?C6AS3H32 (Ettringite)
C-S-H is a poorly crystallized spine formed amorphous crystal with a very small dimension so that
even with an electron-microscope it not observable clearly.
Figure 4. Hydrated Cement Crystals
(Han Aylie, 2009)
Interface Transition Zone (ITZ)
From microscopic view the position of ITZ is
clearly illustrated in figure 5.
CH is a tubular, hexagonal excellent crystallized
mineral. The crystals are large so that they often
can be observed with the naked eye.
Ettringite are good crystallized prismatic needle
formed crystals.
The C-S-H, CH and ettringite crystals influence
the concrete properties at the Interface Transition
Zone (ITZ).
Figure 5. Illustration of ITZ’ position within the
concrete mass
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
2
Diamond and Barnes (1978, 1979) concluded
that the ITZ consist of a duplex film of CH and CS-H crystals having a thickness of 0.5 – 1 ?m. On
top of this layer is the transition zone 50 ?m thick
formed by hollow-shell CH crystals and
ettringite.
Zimbelmann (1978) defined the ITZ in three
layers. The contact layer close to the aggregate
surface 2-3 ?m in thickness consist of CH and
ettringite crystals. On top of this layer is the in-
termediate layer 5-10 ?m, consisting of ettringite
and C-S-H needle-formed crystals and sparingly
distributed flaky CH crystals. Close to the bulk
paste is the dense transition zone 10 ?m in
thickness.
Yang and Guo (1988) found out that the ITZ is a
duplex film formed from CH crystals and a thin
C-S-H layer. The next film is a network of
ettringite and C-S-H crystals having a very high
porosity level (figure 6).
Figure 6. SEM images of hardened concrete (Han Aylie 2009)
Interface strength and its influence on concrete
The interface Transition Zone is recognized as the
“weak link” in concrete (Larbi, 1991, Mindess,
1996, Diamond and Huang, 1998). The weakness
is due to low adhesive strength, highly depending
on the volume size voids in the ITZ (Mehta,
1986) while the characteristics of large crystals
tend to posses less adhesion capacity. These
Calcium Hydroxide crystals have an orientation
that allows cracks to occur along their weak bond
plane. Further, micro cracks tend to propagate
along the weak plane of the crystals following the
Van der Waals forces’ plane.
The ITZ is found to be an intermediate layer
between the aggregate to the hardened cement
mortar (Maso, 1996).
Figure 7. Visualization of the ITZ (Larbi, 1991; Mindess, 2003)
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
3
This intermediate layer has a micro-structural
different composition. The crystal formations
within the layer are highly non-homogeneous.
The distinctiveness of this ITZ layer depends on
various aspects, but among them the aggregate’s
characteristic is the most influential. Physical
properties of aggregate’s affecting the ITZ are
area-to-volume ratio; dimension and porosity
(Mehta, 1986; Mindess, 2003). Figure 7 shows a
diagram of the ITZ for conventional, natural
aggregates.
The present of voids in the cement mortar are
oppositely correlated to the water cement factor
and will decrease in time. These voids will enable
larger crystal to form during the cement
hardening process. Other factors influencing the
ITZ for-mation are the presence of a water film
sur-rounding the aggregates due to bleeding.
At 30 times, the slag has a rougher texture with
more voids, suggesting a better bonding to the
mortar when in compression. At a closer view
however, the surface of slag appears smooth and
fine, having large plates. The Pudak Payung
aggregates on the other hand, demonstrates a
better bond media for the cement mortar.
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
Aggregate Characteristics and SEM Readings
The based on test result (Putra, 2006, Purwono,
Shofianto, 2007) is was shown that physical
properties of slag and natural aggregates are
similar, except that the slag has a slightly higher
density, Los Angeles and Impact value combined
with a lower absorption rate. The slag has
generally a better particle shape with a rougher
texture. The low absorption will more likely lead
to a higher workability. This is explained due to
the presence of unconnected voids. According to
Indonesian Code all values are within the
permissible range.
For the SEM analysis, the samples are observed
based on the Secondary Imaging method. The
reading is performed on the aggregate surface and
along the ITZ’s concrete fracture surface. A layer
of the past is grinded and attached to the platinum
molt, the observed surface remains virgin. A
reading at 250 times is set to localize the
observed the aggregates and ITZ, followed by
readings of 5.000 to 7.500 times. The aggregate
details are presented in figure 8 and 9.
ITZ of slag versus Pudak Payung aggregates
Form visual examination of 28 days test cylinders
it was shown that the percentage of bond failure
within the slag-concrete was noticeable lower
than of the Pudak Payung aggregates. This
finding supported with the SEM readings (figure
10 and 11); confirm that a better ITZ is present at
slag surfaces.
4
Figure 10 shows an approximately 0.1 µm gap
between the aggregate and the cement mortar; the
gap is noticeable smaller for slag concrete. Also
the Pudak Payung ITZ shows a different constitution. A thick layer of C-S-H ranging from 2
to 5 µm confirms the findings of Diamond and
Barnes (1978, 1979); Zimbelmann (1978); Yang
and Guo (1988) and other former researchers.
On top of this layer ettringites and CH crystals
are detected, while round formations are
suggesting the presence of fly-ash in the cement.
This layer expands into the cement mortar.
Diamond and Barnes’s description fits best for
overall the Pudak Payung ITZ.
Observing the slag ITZ (figure 11) it can be seen
that a different structure is present. A gap smaller
than 0.1 µm is observed followed directly by a
dense layer, 5 to 10 µm in thickness probable CS-H crystals. On top of this layer CH crystals are
distinguish, reaching into the cement mortar. No
ettringites or voids are identified.
Conclusion and Future Research
The Interfacial Transition Zone is known as the
weak link in concrete. The behavior of slagconcrete that deviates from normal aggregates
concrete suggest that this deviation is originated
from its ITZ.
When observed with the naked eye, the slag
suggests a better surface for bonding since it has a
rough and irregular surface. But on closer scale
the particles are smooth and shiny while Pudak
Payung has a much better bonding area. Physical
properties’ test results showed that both Pudak
Payung and slag are suitable to be used in
concrete since all Indonesia requirements are met.
The ITZ of Pudak Payung and Slag demonstrate a
significant difference, both constitutional and
dimensional. Further research work is required to
observe crystal growth by testing samples at
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
various ages. Also the tests should include the
addition of silica fume, since this material
improves ITZ performances. Tensile behavior for
all slag types, coarse and fine should be
evaluated.
While the SEM analysis provides only qualitative
data, additional tests such as Sulfate Attack,
Chloride Penetration and Carbonation can
provide the researcher will quantitative data that
can be correlated to the mechanical properties of
concrete.
References
1. Bazantova, Z. and Modry, S., 1998,
“Properties of Interfacial Transition
Zone in Gypsum-Free Cement-Rock
Composites”, Proceedings of the
International RILEM Conference 35,
E and FN Spon, London.
2. Bentur, A. and Alexander, M. G., 2000, “A
Review of the Work of the RILEM TC
159-ETC: Engineering of the interfacial transition zone in cementitious
compositions”, Material and Structures, Vol. 33, March 2000, pp. 8287
3. Besari, M.S., 2007. “Review of Some Vital
Physical Mechanical Parameters of
Concrete”, International Conference
on Material Development in the
Concrete Industry, Jakarta, Indonesia.
4. Darwin, D., 1995, “The Interfacial Transition Zone, Direct Evidence on Compression Response”, Proceedings of
the Material Research Symposium
Vol. 370, Material Research Society,
pp. 419-427.
5. Diamond, D. and Huang, J., 1998, “The
Interfacial Transition Zone: Reality
or Myth?”, The Interfacial Transition
Zone in Cementitious Composites,
Proceeding RILEM Conference in
Haifa, ed. Katz, A and Bentur, A
5
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Han A. L., and Tudjono S., 2008, “The
Study of Concrete with Industrial
Steel-slag Aggregates based on the
Substitution
method”,
5th
International
Conference
on
Concrete, Singapore, August 2008.
Han, A. L. and Tudjono, S., 2007, “PT Inti
General Yaja Slag Replacing PudakPayung Aggregates for Concrete, an
Experimental Research”. Proceeding
of the National Seminar “Steel
Development and Its Impact on
Environmental Issues”, Diponegoro
University- AMBI (Indonesian Steel
Community Association), Semarang,
23 July 2007.
Hsu, T. T. C., and Slate, F. O, Stuurman, G.
M. and Winter G., 1963, “Micro
Cracking of concrete and the shape
of the stress-strain curve”, Journal of
the ACI Proceeding
Kurniawaty, I., 2006, “Pemanfaatan Limbah
Slag yang Mengandung Cr dan Zn
dari Industri Baja dengan Metoda
Solidifikasi sebagai Campuran Beton
untuk Mengurangi Resiko Pencemaran Lingkungan” (Solidification of
Cr and Zn containing slag waste as a
concrete component to incorporate
their environmental impacts), Thesis,
Environmental Engineering Department,
Diponegoro
University,
Semarang.
Larbi, J.A, 1991, “The Cement Paste-Aggregate Interfacial Zone in Concrete”, PhD Dissertation, Delft
University of Technology, The Netherlands
Leonardo, K., Pramono A., Rike, I. and Tirta
A., 2008, “Experimental Research
for the use of Coarse and Fine Slag
Aggregates in Concrete”, Thesis,
Material and Structural Laboratory,
Diponegoro University, Semarang,
Indonesia.
Maso, J.C., 1996, “Interfacial Transition
Zone in Concrete”. RILEM Report
Nr. 11 on Interfacial in Cementitious
Compositions, Toulouse, France
Mehta, P. K., 1986, “Concrete: Structures,
Properties and Materials”, Prentice
Hall
Messazza, F., 1996, “Action of environmental conditions”, Interfacial Transition Zone in Concrete, RILEM
Report 11, London.
Mindess, S., 1996, “Test to determine the
mechanical properties of the interfacial zone”, Interfacial Transition
Zone in Conceret, RILEM Report 11,
London.
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
16. Mindess, S., Young, J. F. and Darwin, D.,
2003, “Concrete”, Second Edition,
Pearson Education Inc, Upper Saddle
River, NJ.
17. Mindess, S; Young, J.F. and Darwin, D,
2002, “Concrete”, Second Edition,
Pearson Education.
18. Monteiro, P.J.M., Maso, J.C. and Ollivier,
J.P., 1985, “The Aggregate-Mortar
Interface”, Cement and Concrete
Research, Vol. 15 Nr. 6, pp. 953-958
19. Neville, A., 2003, “Properties of Concrete”,
Fourth Edition, Prentice Hall, New
Jersey.
20. Perry, C. and Gilliot, J.E., 1977, “The
influence of mortar-aggregate bond
strength on the behavior of concrete
in uniaxial compression”. Cement
and Concrete Research Vol. 7
21. Purwono, L. A. and Nurhayanti, S., 2007,
“Tinjauan Eksperimental Kuat Tekan
Beton Dengan Campuran Limbah
Slag” (Experimental study for
determining the compression strength
of concrete using slag waste), Thesis,
Civil
Engineering
Department,
Diponegoro University, Semarang.
22. Putra, V. S. and Nurhidayati, Z. A., 2006,
“Penelitian Pemanfaatan Limbah
Padat Sebagai Agregat Kasar Pada
Beton” (Solid steel waste as coarse
aggregate
for
concrete,
and
experimental study), Thesis, Civil
Engineering Department, Diponegoro
University, Semarang.
23. Rao, G.A. and Prasad, B.K.R., 2002,
“Influence of the Roughness of
Aggregate Surface on the Interface
Bond Strength”, Cement and
Concrete Research, Vol. 32 pp. 253257.
24. Scivener, K. L. and Pratt, P.L., 1996,
“Characterisation of Interfacial Microstructure”, Interfacial Transition
Zone in Concrete, RILEM Report 11,
London.
25. Scivener, K. L., Crumbie, A. L. and
Laugesen, P, 2004, “The Interfacial
Transition Zone (ITZ) Between
Cement Paste and Aggregate in
Concrete”, Interface Science 12,
Kluwer Academic Publisher, pp 411421.
26. Shofianto and Sutrisno, U. W., 2007,
“Pemanfaatan Slag Limbah Baja
untuk Campuran Beton”, Thesis,
Civil Engineering Department, Diponegoro University, Semarang.
6
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
7
AGGREGATES, PROPERTIES AND THE INTERFACIAL TRANSITION ZONE
Han Ay Lie *)
Abstract
Steel-slag is a residual product of the steel industry that has potential ability to pollute the ground water
and soil containing heavy metals. To overcome this problem, attempts have been made for using the slag as
substitute for both coarse and fine aggregates in concrete. The solidification process will prevent the metal
components from polluting the water and soil.
Test results on the mechanical properties of slag-concrete showed that while the compression strength of
slag-concrete increased significantly as a function of slag-to-natural aggregate’s use, the tensile strength
dropped accordingly.
The substitution of fine-slag to Muntilan sand was even more negative, the compression strength decreased
as a function of slag use. Research into the influences of the Interfacial Transition Zone was conducted,
since the ITZ itself forms a weak link within the concrete matrix.
The SEM tests were performed at the Quarter Laboratory, Department of Geology in Bandung using a
Scanning Electron Microscope type JEOL.
Keywords: slag, fine and coarse aggregates, compression and tensile strength.
Introduction
Research conducted at the Construction and
Material Laboratory, Civil Engineering Department, Diponegoro University (Han and Tudjono,
2008, 2007) concluded the following:
1. Workability of fresh concrete mixes increase
as a function of slag usage resulting in a more
compact concrete with a higher mass density.
2. 28 days compression strength increases as a
function of slag - to-conventiona l -aggregate
percentage (figure 1).
3. The ratio of tensile - to-norma l -concrete
strength decreases as a function of increase in
coarse slag usage (figure 2).
4. Fine slag influences both workability and
compression strength negatively.
Figure 2. Tensile Strength of Slag Concrete (Han,
Tudjono, 2008, 2007)
This research work was accomplished by substituting the Pudak Payung aggregates gradually
by the steel-slag, and by replacing the Muntilan
sand by fine slag. All specimens were tested at
age 28 days.
The deviation of compression-to-tensile-strengthrelation arouses the question as whether the cause
is originated from the nature of aggregates itself
and its Interfacial Transition Zone in concrete.
Figure 1. Compression Strength of Slag Concrete
(Han, Tudjono 2008, 2007)
Cement Hydration and the Interfacial Transition Zone
Concrete is a heterogenic material consisting of
aggregates embedded in a cement matrix. The
me-chanical properties of this material are
influenced by their interaction. Figure 3 shows
the physical appearance and the stress-strain
relationship of concrete making components.
*) Staf Pengajar Jurusan Teknik Sipil Fakultas
Teknik Undip
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
1
Figure 3a. Concrete Cross Sectio
Figure 3b. Stress-Strain relationship
of concrete components
The formation of concrete is a product of cement
hydration. Cement is a chemical component consisting of (CaO)3(SiO2) commonly noted as C3S,
(CaO)2(SiO2) noted as C2S and (CaO)3(Al2O3)
noted C3A (fig. 4).
The hydration process results in C-S-H, CH and
ettringite crystals are as following:
• 2C3S+11H?3CH+C3S2H8
• 2C2S+9H?CH + C3S2H8 or (C-S-H)
Calcium Silicate Hydrate
• C3A+3CSH2+26H?C6AS3H32 (Ettringite)
C-S-H is a poorly crystallized spine formed amorphous crystal with a very small dimension so that
even with an electron-microscope it not observable clearly.
Figure 4. Hydrated Cement Crystals
(Han Aylie, 2009)
Interface Transition Zone (ITZ)
From microscopic view the position of ITZ is
clearly illustrated in figure 5.
CH is a tubular, hexagonal excellent crystallized
mineral. The crystals are large so that they often
can be observed with the naked eye.
Ettringite are good crystallized prismatic needle
formed crystals.
The C-S-H, CH and ettringite crystals influence
the concrete properties at the Interface Transition
Zone (ITZ).
Figure 5. Illustration of ITZ’ position within the
concrete mass
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
2
Diamond and Barnes (1978, 1979) concluded
that the ITZ consist of a duplex film of CH and CS-H crystals having a thickness of 0.5 – 1 ?m. On
top of this layer is the transition zone 50 ?m thick
formed by hollow-shell CH crystals and
ettringite.
Zimbelmann (1978) defined the ITZ in three
layers. The contact layer close to the aggregate
surface 2-3 ?m in thickness consist of CH and
ettringite crystals. On top of this layer is the in-
termediate layer 5-10 ?m, consisting of ettringite
and C-S-H needle-formed crystals and sparingly
distributed flaky CH crystals. Close to the bulk
paste is the dense transition zone 10 ?m in
thickness.
Yang and Guo (1988) found out that the ITZ is a
duplex film formed from CH crystals and a thin
C-S-H layer. The next film is a network of
ettringite and C-S-H crystals having a very high
porosity level (figure 6).
Figure 6. SEM images of hardened concrete (Han Aylie 2009)
Interface strength and its influence on concrete
The interface Transition Zone is recognized as the
“weak link” in concrete (Larbi, 1991, Mindess,
1996, Diamond and Huang, 1998). The weakness
is due to low adhesive strength, highly depending
on the volume size voids in the ITZ (Mehta,
1986) while the characteristics of large crystals
tend to posses less adhesion capacity. These
Calcium Hydroxide crystals have an orientation
that allows cracks to occur along their weak bond
plane. Further, micro cracks tend to propagate
along the weak plane of the crystals following the
Van der Waals forces’ plane.
The ITZ is found to be an intermediate layer
between the aggregate to the hardened cement
mortar (Maso, 1996).
Figure 7. Visualization of the ITZ (Larbi, 1991; Mindess, 2003)
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
3
This intermediate layer has a micro-structural
different composition. The crystal formations
within the layer are highly non-homogeneous.
The distinctiveness of this ITZ layer depends on
various aspects, but among them the aggregate’s
characteristic is the most influential. Physical
properties of aggregate’s affecting the ITZ are
area-to-volume ratio; dimension and porosity
(Mehta, 1986; Mindess, 2003). Figure 7 shows a
diagram of the ITZ for conventional, natural
aggregates.
The present of voids in the cement mortar are
oppositely correlated to the water cement factor
and will decrease in time. These voids will enable
larger crystal to form during the cement
hardening process. Other factors influencing the
ITZ for-mation are the presence of a water film
sur-rounding the aggregates due to bleeding.
At 30 times, the slag has a rougher texture with
more voids, suggesting a better bonding to the
mortar when in compression. At a closer view
however, the surface of slag appears smooth and
fine, having large plates. The Pudak Payung
aggregates on the other hand, demonstrates a
better bond media for the cement mortar.
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
Aggregate Characteristics and SEM Readings
The based on test result (Putra, 2006, Purwono,
Shofianto, 2007) is was shown that physical
properties of slag and natural aggregates are
similar, except that the slag has a slightly higher
density, Los Angeles and Impact value combined
with a lower absorption rate. The slag has
generally a better particle shape with a rougher
texture. The low absorption will more likely lead
to a higher workability. This is explained due to
the presence of unconnected voids. According to
Indonesian Code all values are within the
permissible range.
For the SEM analysis, the samples are observed
based on the Secondary Imaging method. The
reading is performed on the aggregate surface and
along the ITZ’s concrete fracture surface. A layer
of the past is grinded and attached to the platinum
molt, the observed surface remains virgin. A
reading at 250 times is set to localize the
observed the aggregates and ITZ, followed by
readings of 5.000 to 7.500 times. The aggregate
details are presented in figure 8 and 9.
ITZ of slag versus Pudak Payung aggregates
Form visual examination of 28 days test cylinders
it was shown that the percentage of bond failure
within the slag-concrete was noticeable lower
than of the Pudak Payung aggregates. This
finding supported with the SEM readings (figure
10 and 11); confirm that a better ITZ is present at
slag surfaces.
4
Figure 10 shows an approximately 0.1 µm gap
between the aggregate and the cement mortar; the
gap is noticeable smaller for slag concrete. Also
the Pudak Payung ITZ shows a different constitution. A thick layer of C-S-H ranging from 2
to 5 µm confirms the findings of Diamond and
Barnes (1978, 1979); Zimbelmann (1978); Yang
and Guo (1988) and other former researchers.
On top of this layer ettringites and CH crystals
are detected, while round formations are
suggesting the presence of fly-ash in the cement.
This layer expands into the cement mortar.
Diamond and Barnes’s description fits best for
overall the Pudak Payung ITZ.
Observing the slag ITZ (figure 11) it can be seen
that a different structure is present. A gap smaller
than 0.1 µm is observed followed directly by a
dense layer, 5 to 10 µm in thickness probable CS-H crystals. On top of this layer CH crystals are
distinguish, reaching into the cement mortar. No
ettringites or voids are identified.
Conclusion and Future Research
The Interfacial Transition Zone is known as the
weak link in concrete. The behavior of slagconcrete that deviates from normal aggregates
concrete suggest that this deviation is originated
from its ITZ.
When observed with the naked eye, the slag
suggests a better surface for bonding since it has a
rough and irregular surface. But on closer scale
the particles are smooth and shiny while Pudak
Payung has a much better bonding area. Physical
properties’ test results showed that both Pudak
Payung and slag are suitable to be used in
concrete since all Indonesia requirements are met.
The ITZ of Pudak Payung and Slag demonstrate a
significant difference, both constitutional and
dimensional. Further research work is required to
observe crystal growth by testing samples at
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
various ages. Also the tests should include the
addition of silica fume, since this material
improves ITZ performances. Tensile behavior for
all slag types, coarse and fine should be
evaluated.
While the SEM analysis provides only qualitative
data, additional tests such as Sulfate Attack,
Chloride Penetration and Carbonation can
provide the researcher will quantitative data that
can be correlated to the mechanical properties of
concrete.
References
1. Bazantova, Z. and Modry, S., 1998,
“Properties of Interfacial Transition
Zone in Gypsum-Free Cement-Rock
Composites”, Proceedings of the
International RILEM Conference 35,
E and FN Spon, London.
2. Bentur, A. and Alexander, M. G., 2000, “A
Review of the Work of the RILEM TC
159-ETC: Engineering of the interfacial transition zone in cementitious
compositions”, Material and Structures, Vol. 33, March 2000, pp. 8287
3. Besari, M.S., 2007. “Review of Some Vital
Physical Mechanical Parameters of
Concrete”, International Conference
on Material Development in the
Concrete Industry, Jakarta, Indonesia.
4. Darwin, D., 1995, “The Interfacial Transition Zone, Direct Evidence on Compression Response”, Proceedings of
the Material Research Symposium
Vol. 370, Material Research Society,
pp. 419-427.
5. Diamond, D. and Huang, J., 1998, “The
Interfacial Transition Zone: Reality
or Myth?”, The Interfacial Transition
Zone in Cementitious Composites,
Proceeding RILEM Conference in
Haifa, ed. Katz, A and Bentur, A
5
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Han A. L., and Tudjono S., 2008, “The
Study of Concrete with Industrial
Steel-slag Aggregates based on the
Substitution
method”,
5th
International
Conference
on
Concrete, Singapore, August 2008.
Han, A. L. and Tudjono, S., 2007, “PT Inti
General Yaja Slag Replacing PudakPayung Aggregates for Concrete, an
Experimental Research”. Proceeding
of the National Seminar “Steel
Development and Its Impact on
Environmental Issues”, Diponegoro
University- AMBI (Indonesian Steel
Community Association), Semarang,
23 July 2007.
Hsu, T. T. C., and Slate, F. O, Stuurman, G.
M. and Winter G., 1963, “Micro
Cracking of concrete and the shape
of the stress-strain curve”, Journal of
the ACI Proceeding
Kurniawaty, I., 2006, “Pemanfaatan Limbah
Slag yang Mengandung Cr dan Zn
dari Industri Baja dengan Metoda
Solidifikasi sebagai Campuran Beton
untuk Mengurangi Resiko Pencemaran Lingkungan” (Solidification of
Cr and Zn containing slag waste as a
concrete component to incorporate
their environmental impacts), Thesis,
Environmental Engineering Department,
Diponegoro
University,
Semarang.
Larbi, J.A, 1991, “The Cement Paste-Aggregate Interfacial Zone in Concrete”, PhD Dissertation, Delft
University of Technology, The Netherlands
Leonardo, K., Pramono A., Rike, I. and Tirta
A., 2008, “Experimental Research
for the use of Coarse and Fine Slag
Aggregates in Concrete”, Thesis,
Material and Structural Laboratory,
Diponegoro University, Semarang,
Indonesia.
Maso, J.C., 1996, “Interfacial Transition
Zone in Concrete”. RILEM Report
Nr. 11 on Interfacial in Cementitious
Compositions, Toulouse, France
Mehta, P. K., 1986, “Concrete: Structures,
Properties and Materials”, Prentice
Hall
Messazza, F., 1996, “Action of environmental conditions”, Interfacial Transition Zone in Concrete, RILEM
Report 11, London.
Mindess, S., 1996, “Test to determine the
mechanical properties of the interfacial zone”, Interfacial Transition
Zone in Conceret, RILEM Report 11,
London.
TEKNIK – Vol. 30 No. 1 Tahun 2009, ISSN 0852-1697
16. Mindess, S., Young, J. F. and Darwin, D.,
2003, “Concrete”, Second Edition,
Pearson Education Inc, Upper Saddle
River, NJ.
17. Mindess, S; Young, J.F. and Darwin, D,
2002, “Concrete”, Second Edition,
Pearson Education.
18. Monteiro, P.J.M., Maso, J.C. and Ollivier,
J.P., 1985, “The Aggregate-Mortar
Interface”, Cement and Concrete
Research, Vol. 15 Nr. 6, pp. 953-958
19. Neville, A., 2003, “Properties of Concrete”,
Fourth Edition, Prentice Hall, New
Jersey.
20. Perry, C. and Gilliot, J.E., 1977, “The
influence of mortar-aggregate bond
strength on the behavior of concrete
in uniaxial compression”. Cement
and Concrete Research Vol. 7
21. Purwono, L. A. and Nurhayanti, S., 2007,
“Tinjauan Eksperimental Kuat Tekan
Beton Dengan Campuran Limbah
Slag” (Experimental study for
determining the compression strength
of concrete using slag waste), Thesis,
Civil
Engineering
Department,
Diponegoro University, Semarang.
22. Putra, V. S. and Nurhidayati, Z. A., 2006,
“Penelitian Pemanfaatan Limbah
Padat Sebagai Agregat Kasar Pada
Beton” (Solid steel waste as coarse
aggregate
for
concrete,
and
experimental study), Thesis, Civil
Engineering Department, Diponegoro
University, Semarang.
23. Rao, G.A. and Prasad, B.K.R., 2002,
“Influence of the Roughness of
Aggregate Surface on the Interface
Bond Strength”, Cement and
Concrete Research, Vol. 32 pp. 253257.
24. Scivener, K. L. and Pratt, P.L., 1996,
“Characterisation of Interfacial Microstructure”, Interfacial Transition
Zone in Concrete, RILEM Report 11,
London.
25. Scivener, K. L., Crumbie, A. L. and
Laugesen, P, 2004, “The Interfacial
Transition Zone (ITZ) Between
Cement Paste and Aggregate in
Concrete”, Interface Science 12,
Kluwer Academic Publisher, pp 411421.
26. Shofianto and Sutrisno, U. W., 2007,
“Pemanfaatan Slag Limbah Baja
untuk Campuran Beton”, Thesis,
Civil Engineering Department, Diponegoro University, Semarang.
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